package 链表;

/**
 * https://leetcode-cn.com/problems/linked-list-cycle/
 * @author 会玩的洋洋
 *
 */

public class _141_环形链表 {
    /**
     * 快慢指针  对于环形链表的经典问题
     * @param head 目标链表
     * @return boolean
     */
    public boolean hasCycle(ListNode head) {
        if (head == null || head.next == null) {
            return false;
        }
        ListNode slow = head;
        ListNode fast = head.next;
        while (slow != fast) {
            if (fast == null || fast.next == null) {
                return false;
            }
            slow = slow.next;
            fast = fast.next.next;
        }
        return true;
    }
}
